Kinetics of the Gas-Phase Reactions of - and -CHCHOO Criegee Intermediate Conformers with SO as a Function of Temperature and Pressure.

Kinetics of reactions between SO and CHCHOO Criegee intermediate conformers have been measured at temperatures between 242 and 353 K and pressures between 10 and 600 Torr using laser flash photolysis of CHCHI/O/N/SO gas mixtures coupled with time-resolved broadband UV absorption spectroscopy. The kinetics of -CHCHOO + SO are pressure-dependent and exhibit a negative temperature dependence, with the observed pressure dependence reconciling apparent discrepancies between previous measurements performed at ∼298 K. Results indicate a rate coefficient of (4.80 ± 0.46) × 10 cm s for the reaction of -CHCHOO with SO at 298 K and 760 Torr. In contrast to the behavior of the -conformer, the kinetics of -CHCHOO + SO display no significant dependence on temperature or pressure over the ranges investigated, with a mean rate coefficient of (1.18 ± 0.21) × 10 cm s over all conditions studied in this work. Results indicate that the reaction of -CHCHOO with SO competes with unimolecular decomposition and reaction with water vapor in areas with high SO concentration and low humidity, particularly at lower temperatures.